1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus which uses photosensitive microcapsule toner particles.
2. Description of Related Art
It is well known to provide an image forming apparatus which uses a photosensitive medium coated with microcapsules comprising a dyeprecursor and a photo hardening material, etc. For example, such an image forming apparatus is disclosed in U.S. Pat. No. 4,399,209 in which the photosensitive medium is exposed based on image information, the microcapsules coated thereon are hardened, and then a latent image is formed on the photosensitive medium. Afterwards, an image forming paper coated with developer, which reacts with the dyeprecursor and makes color, is overlapped with the photosensitive medium and pressure is applied. The latent image is developed by applying such pressure, and an image is fixed on the image forming paper.
Further, U.S. Pat. No. 4,943,509 discloses another image forming apparatus using the above photosensitive medium. In the apparatus, a photosensitive medium on which a latent image is formed and an image forming paper which is an ordinary paper are overlapped putting a developer layer between them, and are pressurized, so that an image is formed on the ordinary paper. U.S. Pat. No. 5,060,011 shows a similar apparatus.
Furthermore, another image forming apparatus which uses a photosensitive medium which supports the microcapsules utilizes a coloring agent instead of the dyeprecursor discussed above, as disclosed in U.S. Pat. No. 4,783,683 (Japanese Laid-Open Patent Publication No. 62-232652). A recording material including a coloring agent is disclosed in detail in U.S. Pat. No. 4,912,011.
However, each photosensitive medium used in the above image forming apparatuses includes a plastic film layer such as PET (polyethylene terephthalate) film as a supporting layer with photosensitive microcapsules provided thereon. This kind of photosensitive medium is used as a member for aiding image formation and is disposed after use. Therefore, in conventional image forming apparatuses, the plastic film used as the supporting layer, which is not essential to form the image, is consumed in each use. Therefore, the cost for disposable photosensitive medium supplies is high. Thus, the whole cost for forming the image is increased.
Ideally, a reusable photosensitive supporting medium from which the photosensitive microcapsules could easily separate would be desirable in order to reduce costs. However, a clear and accurate image must still be formed. If the microcapsules easily separate from the supporting medium, a blurred image will occur since all of the microcapsule material, including the ruptured walls and hardened microcapsules along with the toner, will transfer to the image recording medium. Thus, it has not been possible to provide a reusable photosensitive supporting medium which creates a clear and accurate image.